Cognitive and Demographic Associations of Dementia‐Related Behavioural Changes in Adults With an Intellectual Disability: Findings From the IDS‐TILDA Study

BACKGROUND: Individuals with intellectual disabilities (ID) are at an increased risk of developing dementia. Early detection is essential for providing appropriate support, yet identifying dementia-related changes is challenging due to pre-existing cognitive impairments. Informant-based adapted tools have been developed to support dementia screening in individuals with ID. Among those, the Dementia Screening Questionnaire for Individuals with Intellectual Disabilities (DSQIID) aims to assess behavioural and functional changes related to dementia. This study aimed to examine the associations between the DSQIID total scores, cognitive performance and demographic characteristics of adults with ID. METHOD: This cross-sectional study included 322 individuals with ID (n Down syndrome [DS] = 55; n non-DS ID = 267). Behavioural and functional changes were assessed using the DSQIID, whereas cognitive functioning was measured with the Test for Severe Impairment (TSI), Brief Praxis Test (BPT) and a semantic verbal fluency task. Negative binomial regression analyses were conducted to explore associations between DSQIID total scores and selected demographic and cognitive variables. RESULTS: Age was significantly associated with behavioural dementia-related changes, as assessed by the DSQIID, whereas ID severity was not associated. Results further showed that participants with DS had significantly higher scores on the DSQIID compared to participants with ID without DS. Higher DSQIID scores were significantly associated with higher semantic verbal fluency performance. CONCLUSIONS: Our findings suggest that caregivers may more readily detect behavioural and functional changes in adults with ID who exhibit relatively good verbal capacities. This study underscores the elevated risk of dementia in adults with DS and highlights the importance of supporting caregivers in recognizing early signs of dementia in adults with ID who exhibit lower verbal capacities. The findings underscore the importance of monitoring behavioural, functional and cognitive changes over time. Further research is needed to explore the associations between reported dementia-related changes and the severity of ID.